1. Field of the Invention
The present invention relates to a light-sensitive composition suitable for producing a presensitized plate for use in making lithographic printing plates (hereinafter referred to as "PS plate(s)"), IC circuits, photomasks or the like and more particularly to a negative working light-sensitive composition comprising a diazonium compound and a polymer binder, which exhibits improved sensitivity on light exposure.
2. Prior Art
Most of the light-sensitive compounds used in negative working light-sensitive compositions are diazonium compounds and most commonly used are diazo resins such as a condensate of p-diazodiphenylamine and formaldehyde.
The light-sensitive composition for producing light-sensitive layers of PS plates can be classified into two groups, one of which simply comprises diazo resins, in other words those free of binders as disclosed in U.S. Pat. No. 2,714,066 and the other of which comprises both diazo resins and binders as disclosed in Japanese Patent Un-examined Publication (hereafter referred to as "J. P. KOKAI") No. Sho 50-30604. However, recently, most of the light-sensitive layers of the PS plates comprise diazonium compounds and polymers serving as binders for the purpose of imparting high printing durability to the plates.
As such a light-sensitive layer, there have been known so-called alkali-developable ones whose unexposed portions are removed (or developed) with an aqueous alkaline developer as disclosed in J. P. KOKAI No. Sho 50-30604 and so-called solvent-developable ones whose unexposed portions are removed (or developed) with an organic solvent type developer, but the former has become of major interest recently from the viewpoint of safety in operation and health of operators. Such development types of the light-sensitive layer are determined principally depending on properties of binders used. As the method for making the binders alkali-soluble, there have been known a method as disclosed in J. P. KOKAI No. Sho 50-30604 which comprises copolymerizing carboxyl group-containing monomers to obtain such a binder and a method as disclosed in U.S. Pat. No. 2,861,058 which comprises reacting hydroxyl groups of polyvinyl alcohol with a cyclic acid anhydride such as phthalic acid anhydride to introduce carboxyl groups into the resultant polymers.
However, light-sensitive compositions comprising such polymers cannot have enough sensitivity to produce a sufficiently acceptable image with a short light exposure time.